GaN HEMT Gate-Drain Diode for Inductive Load Protection
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Solution Overview
Problem
Gallium nitride high electron mobility transistors (HEMTs) lack a suitable diode structure for protecting against energy accumulation in inductive loads, leading to potential device disruption due to the absence of a parasitic diode, and existing protection solutions occupy significant area or require silicon diodes that can diffuse into the GaN layer.
Innovation Solution
A semiconductor device with a gate-drain diode integrated into the substrate, where the anode is connected to the gate electrode and the cathode to the drain electrode, allowing voltage transmission from the drain to the gate, thereby enabling energy dissipation through the channel and protecting the HEMT, while being designed to prevent silicon diffusion using an insulating layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protection element (diode) is connected externally to the HEMT, then the HEMT is protected against energy accumulation in inductive loads, but the protection element occupies a large area
Solution Approach 1:
The patent merges the protection diode function with the HEMT structure by integrating the diode within the element isolation region of the same substrate. The diode shares the substrate and isolation structures with the HEMT, eliminating the need for separate protection elements and reducing overall area occupation while maintaining protection capability against inductive load energy accumulation.
2Ease of manufacture
If a polysilicon diode is formed directly on the GaN layer, then the diode can be integrated, but silicon diffuses into the GaN layer causing contamination
Solution Approach 1:
The patent introduces an insulating layer as an intermediary between the polysilicon diode and the GaN layer. This insulating layer prevents silicon diffusion into the GaN layer during diode formation while still allowing the diode to be formed on the same substrate. The insulating layer acts as a barrier that maintains material purity while enabling integration.
3Adaptability or versatility
If the HEMT operates with inductive loads, then the device can perform power conversion functions, but energy accumulation causes voltage exceedance and element disruption
Solution Approach 1:
The patent converts the harmful effect of energy accumulation in inductive loads into a beneficial protection mechanism. The integrated diode provides a controlled path for dissipating the accumulated energy, preventing voltage exceedance and element disruption. The diode's avalanche region safely consumes the stored energy that would otherwise damage the HEMT.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides effective protection against energy accumulation in inductive loads without significant area occupation, preventing silicon diffusion into the GaN layer and ensuring reliable operation of the GaN-HEMT by incorporating a diode structure within the element isolation region.
Implementation Method 1
an extremely high sheet carrier concentration of 1.0×1013 cm−2 or higher can be obtained in a C-axis direction from spontaneous polarization and piezoelectric polarization generated by deformation resulting from lattice mismatch on a hetero interface of aluminum gallium nitride and gallium nitride
Implementation Method 2
spontaneous polarization and piezoelectric polarization generated by deformation resulting from lattice mismatch on a hetero interface
Implementation Method 3
A MOSFET using Si has an anti-parallel parasitic diode connected between the drain and the source in a device structure. When the MOSFET is turned OFF, energy from the inductive load can be consumed using an avalanche region of the parasitic diode.
Data Source
AI summary
A semiconductor device includes a HEMT and a diode. The HEMT includes: a substrate having a GaN layer as a channel layer generating a two-dimensional electron gas and an AlGaN layer as a barrier layer on the GaN layer; a source electrode on the AlGaN layer ohmic contacting the AlGaN layer; a drain electrode on the AlGaN layer apart from the source electrode and ohmic contacting the AlGaN layer; an inter-layer insulating film on the AlGaN layer between the source electrode and the drain electrode; and a gate electrode on the inter-layer insulating film. The substrate includes an active layer region generating the two dimensional electron gas in the GaN layer. The diode includes an anode electrically connected to the gate electrode and a cathode electrically connected to the drain electrode.